1. Field of the Invention
The present invention relates to a driving method for an ink jet recording head, and more particularly to such a driving method adapted for preventing or resolving the clogging of an ink jet recording head.
2 Related Background Art
In ink jet printers, in order to prevent or resolve the nozzle clogging caused by evaporation of a solvent component such as water from the ink in said nozzle, there has been employed blank ink emission, not intended for printing, before the start of printing operation either after the start of power supply or after a predetermined pause without a printing operation. Such blank ink emission has been conducted by simultaneously energizing all of the driving elements corresponding to plural nozzles the same number of times.
However, plural nozzles tend to show different level of clogging due to the head structure or the ink characteristics. For example, if plural nozzles are arranged along a vertical line, the clogging tends to appear in the lower nozzles. This phenomenon is presumably attributable to the fact that the water evaporates from the ink in different nozzles, and denser ink tends to gather in lower positions.
For this reason the number of ink emissions has been determined to be the number required for restoring the lower nozzles that tend to clog most frequently, and all the driving elements corresponding to the plural nozzles have been simultaneously energized that many times. This operation has the following latent drawbacks:
(1) There is useless consumption of ink, since the driving elements corresponding to the upper nozzles, showing less frequent clogging, are energized in synchronization with those of the lower nozzles; and
(2) In energizing the driving elements of the lower nozzles, which have been clogged and are therefore incapable of emitting the ink, particularly in the bubble jet system utilizing thermal energy, there may remain bubbles generated by the liberation of gas dissolved in the ink, caused by the thermal energy accumulated therein, thus leading to new nozzle clogging.